DE102009008290A1 - Coating a surface of substrate using reactive sputtering process in processing chamber, comprises supplying inert gas and reactive gas into the chamber, and operating double magnetron arranged opposite to substrate with alternating current - Google Patents

Abstract

The method for coating a surface (20) of a substrate (21), comprises supplying an inert gas and a reactive gas into a processing chamber (2), operating a double magnetron (3) arranged opposite to the substrate with alternating current, and separating a stoichiometric oxide coating. The partial pressure of the reactive gas is locally reduced in a surrounding area (7) of the double magnetron. The double magnetron is operated in the constant electrode power and the regulation of the reactive gas flow in a reactive-gas-poor metallic mode or within a metal-rich region of a transition mode. An independent claim is included for a device for coating a surface of a substrate using a reactive sputtering process.

Description

The The invention relates to a method for coating a surface of a substrate by means of a reactive sputtering process The preamble of claim 1. Furthermore, the invention relates to a Apparatus for carrying out this method after Preamble of claim 2.

The Coating of surfaces by means of sputtering processes is known. In this case, using an inert gas, in particular Argon, particles ejected from a target and onto a substrate surface where they condense and form a layer. As an ion source serves either a DC gas discharge (DC sputtering) or an alternating field (AC sputtering).

If in addition to the electric field at the location of the target also a magnetic field is applied, one speaks of magnetron sputtering. At the same process pressure can increase the sputtering rate and thus achieved an increase in the coating rate become.

If dielectric or low-conductivity compounds of metals and semiconductors, for example oxides such as SiO ₂ , Al ₂ O _3, etc., are to be produced on the substrate, then a reactive sputtering process is used. In reactive sputtering, a reaction gas is supplied in addition to the inert gas to produce a desired chemical compound. The composition of the coating on the substrate surface can be adjusted by varying the relative pressures of the inert and reactive gases. The reactive sputtering allows coating with materials that are difficult or impossible to atomize in the form of these compounds. Thus, for example, a target consisting of Al ₂ O ₃ can only be sputtered at high frequency and then only at low rates, while sputtering of aluminum with both direct and alternating voltage at high rates is possible. However, the sputtering process comes to a halt in a reactive atmosphere, because on the target surface electrically non-conductive aluminum oxide is formed, which prevents the escape of electrons. This oxide layer also results in changes to the process parameters and requires frequent cleaning or replacement of parts of the device. The formation of aluminum oxide on the target surface also causes electrical charges and, as a result, flashovers and arcing, leading to instabilities in the sputtering process.Soccurrent sputtering additionally has the disadvantage of protecting the anode from dielectric coating which is insufficiently successful and leads to additional arcing Arcing is always associated with instability and particle contamination and therefore needs to be avoided as much as possible.

To counter this problem, is in the DE 40 42 287 A1 proposed to provide in the processing chamber two formed as magnetron cathodes, electrically insulated from each other electrodes which are connected in such a manner to an AC power supply that each of the two cathodes in a period of the AC voltage acts as a negative electrode and a positive electrode, so that the plasma discharge occurs in the sputtering process mainly between the two cathodes. The two targets thus act alternatively as the cathode and anode. A third terminal of the AC power supply is connected to the negative pole of a DC power supply to the positive pole of which a third electrode acting as an anode is connected to maintain the voltage level of the AC power source at a high negative value. Capacities are provided between the targets and the magnetron cathodes which inhibit the electrical flashovers between the targets and their environment and short circuit the radio frequency voltage and current oscillations induced by the sputtering plasma, which can otherwise lead to flashovers and arcing.

Although in the DE 40 42 287 A1 described design of Doppelmagnetrons and its AC power reduces the occurrence of instabilities and arcing, so deposited on the target dielectric material, which can cause flashovers. To reduce such dielectric deposits on the targets is in the US 5,814,195 proposed to run the targets as rotating tubes; Due to the rotation of the targets, changing areas of the pipe surface are used as erosion zones, so that the dielectrics deposited there are removed and the pipe surface is continuously cleaned of deposits. The use of rotating tube cathodes reduces arcing due to dielectric deposits on the target and limits itself to the end regions of the tube targets.

Depending on the amount of reactive gas supplied and the amount of AC voltage applied to the double magnetron, the sputtering apparatus can be operated in different modes of operation (see 2a ): At high voltage and low reactive gas flow, a metal-rich (or semiconductor-rich) mixture is deposited on the substrate. An operation of the sputtering in this so-called "metal mode" has a high stability and high growth rates, but is not suitable for applying dielectric layers, since the stoichiometric composition tion of the deposited layer has too high a proportion of the metal (or semiconductor) material. Although the desired stoichiometric oxide or oxynitride layer is produced on the substrate at low voltage and high reactive gas flow, this so-called "oxide mode" is characterized by low growth rates in a medium voltage and reactive gas flow region between "metal mode" and "oxide mode "exists a so-called" transition mode ", which is unstable and therefore a process-safe operation of the sputtering system is not accessible. Although in principle in a partial pressure-controlled sputtering process (ie, with constant voltage and regulation of the reactive gas partial pressure) in the middle part of the "transition mode" with medium growth rates, a stoichiometric oxide layer can be applied (see 2 B ), but this area is difficult to control in terms of control technology; long-term stability and layer homogeneity (constant layer thickness, stoichiometry and absorption) can generally not be achieved, especially with long cathodes for large surfaces. In the case of planar cathodes, furthermore, considerable instabilities occur along the cathode, caused by arcing at resulting dielectric areas on the target.

in the As a rule, reactive sputtering systems are therefore used in "oxides Mode "with constant power and flow control of the reactive gas supply operated, since this area is technically straightforward and the deposition of a dielectric layer of the desired stoichiometric composition allows - albeit with the disadvantage of very low growth rates.

task The invention is to realize a method and a device, the an increase in the rate of growth while simpler and easier long-term stable process control to achieve the desired Allow layer properties and prevent arcing.

The The object is solved by the features of claims 1 and 2. Advantageous embodiments are the subject of the dependent claims.

After that In the reactive sputtering process, the reactive gas partial pressure becomes in the processing chamber adjusted in such a way that in a double magnetron environment, a locally reduced reactive partial pressure prevails. This local reduction of the reactive partial pressure in the Surrounding the target electrodes causes the double magnetron in metal-rich "Metal Mode" or a metal-rich transition mode ("Transition Mode"). Compared to "oxides Mode ", which is conventionally used in sputtering plants stoichiometric oxide and oxynitride layers used (as it was characterized by a reactive gas surplus is and control technology is easy to control), can in "Transition Mode" or "Metal Mode" much higher growth rates be achieved. Since the reduction of the reactive partial pressure to a Surrounded by the magnetron, prevails in the field of Substrate surface of the "normal" for the preparation of the dielectric coating required reactive partial pressure, so that there are compounds of the desired stoichiometric Composition are deposited.

Of the Operation of the sputtering system in the "transition mode" is known technically difficult to control. Surprisingly possible however, the use of a bipolar double magnetron, the locally reduced reactive partial pressure in an environment sputtering with high process stability, good Stratification and the advantage of high growth rates. While in the region of the substrate surface, a relatively high reactive gas partial pressure so that the reactive gas on the substrate surface with the sputtered from the target particles the desired Stoichiometric layer (in particular an oxide or Oxinitride layer) is in the environment of Doppelmagnetrons the reactive gas partial pressure is greatly reduced. Since the reactive gas partial pressure a decisive influence on the sputter yield at the target has (and in particular the sputter yield with increasing reactive gas partial pressure decreases sharply), causes the local reduction of the reactive partial pressure in the region of the target a high sputter yield. In the inventive Procedure, the target is thus in the "metal mode" or in held a metal-rich area of "transition mode", while in the region of the substrate surface a reactive gas-rich Atmosphere exists for the generation of the desired stoichiometry is necessary.

The inventive method is characterized a high process stability. One reason for this is apparently in the dual function of the AC powered Doppelmagnetrons, whose individual electrodes alternately as a cathode and act as an anode. By generated between the individual electrodes Fields become electrons in the magnetic field from one magnetron to another Magnetron led to the substrate area, thereby an intense plasma built up to the substrate surface and layering is supported. This effect can be amplified when between the electrodes the Doppelmagnetrons a partition is provided.

In a development of the method, depending on the geometry and arrangement of the getter surfaces, a stoichiometric connection in a "metal mode" or a "transition mode" flow-controlled, without partial pressure control or by a stable, in particular relatively slowly operating partial pressure control at a very high rate.

A inventive device for implementation of the reactive sputtering method is in the vicinity of the double magnetron a getter material, which is the Reaktivgaspartialdrucks in the environment locally reduced by double magnetron. This is advantageous Double magnetron surrounded by a shielding, whose the Double magnetron provided adjacent walls with Getterflächen are. The arrangement and geometry of the getter surfaces together with the arrangement and geometry of the reactive gas inlet cause a gradient of the reactive gas during sputtering between the substrate surface and the target surface: On the one hand prevails in the area of the substrate surface relatively high reactive gas partial pressure, so that the reactive gas to the substrate surface with the sputtered from the target Particles the desired stoichiometric coating can form. On the other hand, the getter surfaces bind very well a lot of reactive gas and thus reduce the reactive gas partial pressure in the area of the target surface. Depending on the geometry and Arrangement of Getterflächen can be a stoichiometric Connection without partial pressure control or by a stable slow working partial pressure control deposited at a very high rate become. To measure the reactive partial pressure, a probe may be provided whose measured values are used for partial pressure control.

advantageously, has the shielding a between the double magnetron and arranged on the substrate shielding plate with an opening whose width is less than the total width of the double magnetron. The reactive gas is supplied to the processing chamber through an inlet, on the side facing away from the double magnetron side of the shielding plate is arranged so that the reactive gas between the shield of the Shielding device and the substrate is initiated. The shielding plate limits the rate of penetrating into the shielding Reactive gas. Conveniently, the reactive gas supply multiple inlets, their flow rates individually are controllable.

The Electrodes of Doppelmagnetrons are advantageously as rotating Pipe electrodes designed to the deposition of dielectric impurities to be kept as low as possible. It is understood that also a double magnetron with planar electrodes of of the invention is included.

Farther it has proved to be advantageous to double magneton in one To operate medium frequency range. The side walls of the Shielding device are advantageously arranged with symmetrical Suction openings provided to both electrodes of the double magnetron to set symmetrical pressure conditions. For evacuation the processing chamber are expediently provided at least two high-vacuum pumps whose mouths are arranged symmetrically to the electrodes of the Doppelmagnetrons.

by virtue of the low reactive gas partial pressure in the region of the targets can several Doppelmagnetrons, for example, in an inline plant without additional gas separations, such as gap locks arranged side by side (pump - double magnetron - pump - double magnetron - pump - etc.), which considerably reduces the plant length and costs of the plant.

in the The following is the invention with reference to an illustrated in the figures Embodiment explained in more detail. Showing:

1 a schematic sectional view through an apparatus for reactive deposition of layers using the magnetron sputtering;

2a a schematic reactive gas flow / voltage diagram of a flux-controlled sputtering device with different modes;

2c a schematic reactive gas flow / voltage diagram of a partial pressure-controlled sputtering device with different modes;

2c a schematic Reaktivgasfluss- / voltage diagram of a flux-controlled sputtering device according to the invention.

In The drawings are corresponding elements with each other Reference numeral. The drawings illustrate a schematic embodiment and do not reflect specific parameters of the invention. Furthermore, the drawings are merely illustrative an advantageous embodiment of the invention and should not be interpreted in such a way that they are the Restrict the scope of the invention.

1 shows a schematic sectional view of a device according to the invention 1 for the reactive deposition of layers by magnetron sputtering. The device 1 includes a processing chamber 2 in which a double magnetron three is arranged. The double magnetron three includes two stationary magnet arrangements 6 . 6 ' that of rotating tubular electrodes 4 . 4 ' from a target material 5 are surrounded. Between the electrodes 4 . 4 ' of the double magnetron three is a partition 8th arranged.

To power the Doppelmagnetrons three is a bipolar power supply unit 10 provided, which is operated at medium frequency. Details of the structure and operation of such an AC power supply unit 10 are the US 5,814,195 whose disclosure content is hereby incorporated into the present patent application.

In the vicinity of the double magnetron three there are inlets 14 for an inert gas, in particular argon, with a distribution unit, from which the inert gas acting as a sputtering gas to the electrodes 4 . 4 ' of the double magnetron three is directed; the resulting flow is indicated by small arrows. To control the inert gas supply are (in 1 not shown) control valves provided.

In a double magnetron three opposite region of the processing chamber 2 is at a distance D _SM a substrate to be coated 21 on one (in 1 not shown) substrate holder arranged. If the substrate 21 is a heat-sensitive plastic film, the substrate holder may be provided with a cooling device.

In the processing chamber 2 is still a shielding device 30 arranged, which is the double magnetron three surrounds and the flow of the electrodes 4 . 4 ' knocked out target particles laterally limited. The shielding device 30 includes side walls 31 at a distance D _WM from the double magnetron three are arranged, and a shield 32 that is between the double tube magnetron three and the substrate 21 located and with an opening 35 is provided for the passage of the target particles. In one between the shielding plate 32 and an intermediate sheet 33 the shielding device 30 formed cavity 34 There are several gas inlets 15 , via which a reactive gas, in particular O ₂ , into the processing chamber 2 can be supplied; the reactive gas flow is in 1 indicated by small arrows. As the shielding 32 deeper into the interior of the shielding device 30 protrudes as the intermediate plate 33 , that gets out of the cavity 34 flowing reactive gas preferably in the direction of the substrate 21 directed. In another cavity 36 , between the intermediate sheet 33 and a cover plate 37 the shielding device 30 are inlets 38 for an inert gas, in particular argon, provided by means of which the reactive gas flow can be selectively influenced. To a given distribution of the reactive gas in the processing chamber 2 to reach are the reactive gas inlets 15 with individually adjustable flow regulators 16 Mistake. Instead of separate inlets 15 . 38 for reactive and inert gas can be via the inlet 15 Also, a mixture of a reactive and an inert gas are supplied.

Furthermore, lambda probes are in the processing chamber 40 arranged to measure the O ₂ partial pressure. The measured values of the lambda probes 40 become a regulatory device 41 fed, with which the reactive gas flow regulator 16 or the inert gas 38 can be adjusted in such a way that in the region of the substrate surface 20 a given local O ₂ partial pressure prevails.

Preferably is the Reaktivgaspartialdruck depending on the Reaktivgasfluß or the sputtering power regulated. Furthermore, means for measuring be provided the sputtering voltage. The control device can also be designed to control the sputtering voltage, preferably the Sputter voltage as a function of the reactive gas flow or the sputtering power is adjustable.

In the wall of the processing chamber 2 are in one outside the shielding device 30 located area connections 18 for high vacuum pumps 19 intended. The side walls 31 the shielding device 30 have suction openings 25 in order to pump out the interior of the shielding device 30 to facilitate.

The shielding device 30 is in the double magnetron three facing inner surfaces 51 . 52 the side walls 31 and the shielding plate 32 at least in sections with getter surfaces 50 provided that sorb reactive gas and thus reduce the local reactive gas partial pressure. By the design of the shielding device 30 and their getter surfaces 50 will be between the surface 20 of the substrate 21 and an environment 7 the target electrodes 4 . 4 ' achieved a partial pressure gradient of the reactive gas, so that in the environment 7 of the double magnetron three a reduced reactive gas partial pressure prevails. For this purpose, in particular the width B _{A of} the opening 35 of the shielding plate 32 in such a way that B _A / B _M ≤ 0.9 (and preferably ≤ 0.8), where B _{M is} the width of the double magnetron three designated. Furthermore, the distance D _AM between the shield 32 and the double magnetron three in such a way that D _AM / D _SM ≤ 0.7 (and preferably ≤ 0.6), where D _{SM is} the distance between substrate surface 20 and double magnetron three designated. In addition, the distance D _ST between the substrate surface 20 and the partition 8th in such a way that 0.3 ≦ D _ST / D _SM ≦ 0.5. Typically, the tube electrodes have 4 . 4 ' an outer diameter B _E ≈ 140-160 mm and the double tube magnetrons three a total width B _M ≈ 350-380 mm, and the distance D _SM between substrate surface 20 and double tube magnetron three is typically D _SM ≈ 100 mm; in such a case, the width B _{A of} the opening should 35 in the shielding plate 32 preferably at B _A ≤ 320 mm and the distance D _AM between the shield 32 and double tube magnetron three preferably at D _AM ≤ 70 mm. Furthermore, the distance D _{WM should be} between the side wall 31 the shielding device 30 and the double tube magnetron three at least 5 mm.

The getter surfaces 50 can - as in 1 shown - the inner surfaces 51 . 52 the side walls 31 and the shielding plate 32 cover the shielding device. In this case, the side walls exist 31 and the shielding plate 32 preferably of a metal sheet coated with getter material. Alternatively, the getter surfaces 50 are formed by sintered getter elements attached to the inner surfaces 51 . 52 the side walls 31 and / or the shielding plate 32 are attached. The getter surfaces 50 but can also directly the inner surfaces of the side walls 31 and the shielding plate 32 the shielding device. The on the Getterflächen 50 impinging target particles bind a lot of reactive gas and thereby cause the reduced reactive gas pressure at the surface of the target electrodes 4 . 4 ' ,

When Getter materials can in particular Mo, Zr, Ti, Ta, V and alloys of these metals or alloys with other metals are used, such. As Ti-V, Zr-V, Zr-Al, Zr-V-Fe, etc. but also Al, Cu as well as alloys with other metals and plasma sprayed Coatings, z. Al.

Of the crucial getter is the growing shift and not one existing getter material. An existing getter material or Getter coating can serve a good adhesion of the growing up Layer z. B. by a rough surface, an adapted thermal expansion coefficient or temperature stabilization by To ensure cooling.

The getter surfaces 50 adsorb reactive gas and cause the reactive gas partial pressure in the interior of the shielding device 30 so in the environment 7 of the double magnetron three , locally diminished. This means that the target electrodes 4 . 4 ' can be operated in the reactive gas-poor "metal mode" or in a metal-rich region of the "transition mode" (ie in an in 2c schematically illustrated work area 60 , at constant electrode power and control of the reactive gas flow). The geometry and arrangement of the getter surfaces 50 is designed so that at the substrate surface 20 a stoichiometric compound with high growth rate can be deposited. In this way, a very stable and easy-to-regulate coating process can be achieved.

The device 1 is particularly suitable for depositing dielectric layers such as SiO ₂ and / or Al ₂ O ₃ and their oxynitrides and mixtures on large areas in in-line sputtering.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 4042287 A1 [0005, 0006]
• US 5814195 [0006, 0027]

Claims (19)

Method for coating a surface ( 20 ) of a substrate ( 21 ) by means of a reactive sputtering process in a processing chamber ( 2 ), - wherein an inert gas and at least one reactive gas in the processing chamber ( 2 ) ( 14 . 15 ), - and one opposite to the substrate ( 21 ) arranged double magnetron ( three ) is operated with alternating current, characterized in that - the partial pressure of the at least one reactive gas in an environment ( 7 ) of the double magnetron ( three ) is locally reduced. Method according to claim 1, characterized in that the dual magnetron ( three ) is operated at constant electrode power and control of the reactive gas flow in a reactive gas-poor metallic mode or in a metal-rich region of a transition mode. Method according to claim 2, characterized in that that a stoichiometric oxide layer is deposited. Contraption ( 1 ) for coating a surface ( 20 ) of a substrate ( 21 ) by means of a reactive sputtering process, - with a in a processing chamber ( 2 ) arranged double magnetron ( three ) with two electrodes ( 4 . 4 ' ), - with a bipolar power supply unit ( 10 ), - with one in the processing chamber ( 2 ) reactive gas feed ( 15 ) and one into the processing chamber ( 2 ) inert gas feed ( 14 ), characterized in that - in an environment ( 7 ) of the double magnetron ( three ) Gettering surfaces ( 50 ) are provided for the local reduction of the reactive gas partial pressure. Device according to claim 2, characterized in that the double magnetron ( three ) of a shielding device ( 30 ) on which the double magnetron ( three ) adjacent inner surfaces ( 51 . 52 ) Gettering surfaces ( 50 ) are provided. Apparatus according to claim 2 or 3, characterized in that the shielding device ( 30 ) between the double magnetron ( three ) and the substrate ( 21 ) arranged shielding plate ( 32 ) with an opening ( 35 ) having. Device according to one of claims 2 to 4, characterized in that the walls ( 31 ) of the shielding device ( 30 ) Suction openings ( 25 ) exhibit. Device according to one of claims 2 to 5, characterized in that the reactive gas supply a plurality of inlets ( 15 ) with individual flow regulators ( 16 ) are provided. Device according to one of claims 2 to 6, characterized in that the at least one inlet ( 15 ) of the reactive gas supply between the shielding plate ( 32 ) of the shielding device ( 30 ) and the substrate surface ( 20 ) is arranged. Device according to one of claims 2 to 7, characterized in that the double magnetron ( three ) rotating tube electrodes ( 4 . 4 ' ). Device according to one of claims 2 to 8, characterized in that the AC power supply of Doppelmagnetrons ( three ) takes place in the middle frequency range. Device according to one of claims 2 to 9, characterized in that between the electrodes ( 4 . 4 ' ) of the double magnetron ( three ) a partition wall ( 8th ) is provided. Device according to one of claims 2 to 10, characterized in that the device ( 1 ) at least one high vacuum pump ( 19 ) whose supply line ( 18 ) outside the shielding device ( 30 ) into the processing chamber ( 2 ) opens. Device according to one of claims 2 to 11, characterized in that in the processing chamber ( 2 ) a probe ( 40 ) is provided for measuring the Reaktivgaspartialdrucks. Device according to one of claims 2 to 12, characterized in that a control device ( 41 ) is provided for controlling the reactive gas partial pressure. Device according to claim 13, characterized in that that the reactive gas partial pressure by means of the reactive gas or is controllable by means of the sputtering power. Device according to one of claims 2 to 11, characterized in that means for measuring the Sputtering voltage are provided. Device according to one of claims 2 to 15, characterized in that a control device ( 41 ) is provided for controlling the sputtering voltage. Device according to Claim 16, characterized in that the sputtering voltage is regulated by means of the reactive gas flow or by means of the sputtering power bar is.